The protein encoded by this gene belongs to the highly conserved cyclin family, whose members are characterized by a dramatic periodicity in protein abundance through the cell cycle. Cyclins function as regulators of CDK kinases. Different cyclins exhibit distinct expression and degradation patterns that contribute to the temporal coordination of each mitotic event. This cyclin tightly associates with CDK9 kinase, and was found to be a major subunit of the transcription elongation factor p-TEFb. The kinase complex containing this cyclin and the elongation factor can interact with, and act as a cofactor of human immunodeficiency virus type 1 (HIV-1) Tat protein, and was shown to be both necessary and sufficient for full activation of viral transcription. This cyclin and its kinase partner were also found to be involved in the phosphorylation and regulation of the carboxy-terminal domain (CTD) of the largest RNA polymerase II subunit.
^Wei P, Garber M, Fang S, Fischer W, Jones K (March 1998). "A novel CDK9-associated C-type cyclin interacts directly with HIV-1 Tat and mediates its high-affinity, loop-specific binding to TAR RNA". Cell92 (4): 451–62. doi:10.1016/S0092-8674(00)80939-3. PMID9491887.
^Tian Y, Ke S, Chen M, Sheng T (November 2003). "Interactions between the aryl hydrocarbon receptor and P-TEFb. Sequential recruitment of transcription factors and differential phosphorylation of C-terminal domain of RNA polymerase II at cyp1a1 promoter". J. Biol. Chem.278 (45): 44041–8. doi:10.1074/jbc.M306443200. PMID12917420.
^De Falco G, Bagella L, Claudio P, De Luca A, Fu Y, Calabretta B et al. (January 2000). "Physical interaction between CDK9 and B-Myb results in suppression of B-Myb gene autoregulation". Oncogene19 (3): 373–9. doi:10.1038/sj.onc.1203305. PMID10656684.
^Fu T, Peng J, Lee G, Price D, Flores O (December 1999). "Cyclin K functions as a CDK9 regulatory subunit and participates in RNA polymerase II transcription". J. Biol. Chem.274 (49): 34527–30. PMID10574912.
Cunningham A, Li S, Juarez J, Lynch G, Alali M, Naif H (2000). "The level of HIV infection of macrophages is determined by interaction of viral and host cell genotypes". J. Leukoc. Biol.68 (3): 311–7. PMID10985245.
Minghetti L, Visentin S, Patrizio M, Franchini L, Ajmone-Cat M, Levi G (2004). "Multiple actions of the human immunodeficiency virus type-1 Tat protein on microglial cell functions". Neurochem. Res.29 (5): 965–78. doi:10.1023/B:NERE.0000021241.90133.89. PMID15139295.